Sigil was originally created for Planescape as the setting's "home base". According to Steve Winter in ', "A movable base, like a vessel of some sort wouldn't do it. It had to be a place that characters could come home to when they needed to, and it had to be central to the nature of the setting." Sigil's fifteen factions were created because, "' was a particularly hot game at time and one of the ideas in it that we really liked was the clans. Jim Ward wanted to be sure that players had something to identify with and to give them a sense of belonging in this alien venue ." Scott Haring, in his review of the Planescape Campaign Setting for Pyramid, described Sigil as "a strange city with doors to every plane and every reality, and inhabitants from all those planes and realities living together in harmony." Trenton Webb of British RPG magazine Arcane calls the city "splendidly bizarre" and declares that "Sigil, The Lady of Pain's citadel, is an elegant gaming construct, yet it can often feel a little hollow", feeling that life in Sigil should be "a swirl of plots, factions and sedition that leaves players' heads spinning, wounds bleeding and experience points tally in overdrive".Trenton Webb reviewed Uncaged: Faces of Sigil for Arcane magazine, rating it a 9 out of 10 overall.
Sigil is first described in the Planescape Campaign Setting boxed set, released in 1994. It is also featured prominently in some later Planescape rulebooks, including ', The Factol's Manifesto, and ', as well as in many adventures, such as The Eternal Boundary, Harbinger House, and Faction War.
''Dungeons & Dragons'' 3.5 edition (2003–2008)
A short description of Sigil is in this edition's Dungeon Master's Guide. Information on Sigil can also be found in various 3.0 and 3.5 sourcebooks, such as the Manual of the Planes and the Planar Handbook. A small reference to Sigil is also done in the Epic Level Handbook aside other planar metropolis such as Tu'narath.
''Dungeons & Dragons'' 4th edition (2008–2014)
Sigil is described in the 4th edition Manual of the Planes and expanded upon in Dungeon Master's Guide 2. The City of Doors, unlike many planes, remains almost completely unchanged from earlier editions.
''Dungeons & Dragons'' 5th edition (2014–)
Sigil is briefly mentioned in Appendix C of the 5th edition's Player Handbook. There is also some information on Sigil in Dungeon Master's Guide at the end of Chapter 2.
Sigil is located above the tall Spireat the center of the Outlands. It has the shape of a torus; the city itself is located on the inner surface of the ring. There is no sky, simply an all-pervasive light that waxes and wanes to create day and night. Sigil cannot be entered or exited save via portals; although this makes it quite safe from any would-be invader, it also makes it a prison of sorts for those not possessing a portal key. Thus, sometimes Sigil is called "The Cage". Though Sigil is pseudo-geographically located "at the center of the planes", scholars argue that this is impossible since the planes are infinite in all dimensions, and therefore there can never truly be a center to any or all of them; thus, Sigil is of no special importance. Curiously, from the Outlands one can see Sigil atop the supposedly infinite Spire. Sigil contains innumerable portals that can lead to anywhere in the Dungeons & Dragons cosmology: any bounded opening could possibly be a portal to another plane, or to another point in Sigil itself. Thus, the city is a paradox: it touches all planes at once, yet ultimately belongs to none; from these characteristics it draws its other name: "The City of Doors". Sigil is ruled by the Lady of Pain. Sigil is also highly morphic, allowing its leader to alter the city at her whim. Theoretically, Sigil is a completely neutral ground: no wars are waged there and no armies pass through. Furthermore, no powers are allowed to enter the city.
In other media
Sigil is also the setting for the 1999 video gamePlanescape Torment, in which the player is the immortal "Nameless One." The team chose to place the game around a central fixture of Planescape, the city of Sigil, and the game begins with the character waking up on a cold stone slab in the Mortuary of Sigil, with no idea of who he is, what he is doing there or how he died. In an interview with RPGWatch, Chris Avellone commented on the use of Sigil as the game's main setting, saying "We felt Sigil was the part of Planescape we really had to get right from the outset in case we made more games. It's the signature city, but... we did sacrifice other planar locations so that we could do it."
